The prior arts to which a nail clipper of the invention is directed are disclosed in U.S. Pat. No. 6,173,497, Japanese Patent Laid-Open Publication No. (Hei) 11-169227 (Jun. 29, 1999), U.S. Pat. No. 796,389, U.S. Pat. No. 806,037, U.S. Pat. No. 5,488,772, Japanese Utility Model Laid-Open Publication No. (Sho) 57-27204 (Feb. 12, 1998), International Publication No. WO 02/067720, and International Publication No. WO 02/39844 (counterpart application: Japanese Patent Laid-Open Publication No. 2002-142853).
U.S. Pat. No. 6,173,497, which is related a rotation operating structure of a nail cutter applied to the invention, discloses a constitution that a jaw is connected to handles through hooked ends, and the jaw is rotated from the handles. However, according to the nail clipper of that invention, there is an inconvenience in that the two handles should be folded and unfolded upon use. Further, since the nail clipper has no structure for setting an angle of the cutter, there is no means for preventing the cutter from easily and freely being rotated upon using. Furthermore, in case that the jaw is made of a single piece construction, there is no means for making a flexible elasticity or for reinforcing rigidity. Also, since both levers are constituted to face each other at both sides when closing the jaw up and down, there has been an inconvenience for manipulating the rotation of the jaw.
A first embodiment of Japanese Patent Laid-Open Publication No. (Hei) 11-169227 discloses a cutter or a jaw constituted to be rotated by a desired angle. However, since the cutter is inserted between an upper plate and a lower plate of a supporting member or a body, there has been an inconvenience that, upon rotating the cutter, a user pushes the cutter from the body using a finger, and then manipulates again the cutter to adjust to a desired revolution angle. Meanwhile, according to a second embodiment, since a lower part of the cutter is opened, the cutter can be directly rotated. However, since a rear end of the cutter is coupled to the body by a rivet, the rotation movement is not easily made. Further, if a user uses the nail clipper with the cutter rotated, since the user presses the lever with the body and the lever crossed each other, there have been drawbacks that the pressing motion is unnatural, and a force for cutting a nail is deflected.
U.S. Pat. No. 796,389 and U.S. Pat. No. 806,037 commonly comprise a cutter and a lever for manipulating the cutter. According to a structure of the cutter, since the cutter is made by simply bending a plate and forming a cutting blade of a front end thereof, a rigid structure of the cutter or an elastic flexible operation structure of the cutter is not disclosed. In such a case, there have been problems as follows.
In case of biting motion (motion for cutting a nail) of both blades by manipulating a lever, since the cutter is very thin, and thus has a weak rigidity, the cutter is bent, whereby the cutting force is weakly transferred. To prevent this, a plate thickness of the cutter should be increased. However, in such a case, since a center portion of the bent part becomes rigid, and thus a motion for pressing the cutter is not smooth, and a manipulation of the lever becomes difficult. Therefore, if the force for pressing the cutter is directly transferred to a blade portion, and acts as a shearing force, means for having opposite properties that the cutter should have a rigidity and a flexible elastic force is requested.
According to U.S. Pat. No. 5,488,772, a cutter has a sidewall projected from one side thereof. However, since this constitution is only for supporting a pin of a lever, and it is not for a reinforcing structure, the above problems discussed above with reference to U.S. Pat. No. 796,389 and U.S. Pat. No. 806,037 still remains.
According to Japanese Utility Model Laid-Open Publication No. (Sho) 57-27204, upper and lower cutters have sidewalls at both sides thereof for the purpose of preventing a cut nail from scattering, respectively. However, since this constitution does not suggest a means for providing flexible elasticity, it is not practically used.
Further, International Publication No. WO 02/067720 discloses a nail clipper having a cutter, and a lever for manipulating the cutter, but this constitution is not for rotating the cutter. Meanwhile, the cutter comprises an elastic part constituted by penetrating a circle hole in a center of a bent plate member, and a rigid part having a wide width and a slightly bent shape. However, in such a case, there have been problems as follows. In the process of manufacturing a nail clipper, a cutter has a high hardiness through a heat treatment process for endurance of a blade after a press process. In case of forming the upper and lower cutters by bending a center portion of the cutter, which is made of the material described above, having a short length, a stress pressing repeatedly upon using is concentrated upon the center portion of the bent part, specifically, the narrowest portion of the center portion. Thus, a breakage is easily generated, whereby the nail clipper cannot be used. According to the claims of that invention, number and size of hole requested for a proper resilience may be adjusted. Thus, this means that a proper resilience is provided. However, since the method for widely dispersing the repeated stress is not suggested, the breakage of the cutter due to the stress concentration phenomenon cannot be prevented. Further, in order to maintain a rigid section, a resilient section is extremely limited on the center portion of the bent part by forming a reinforcing rib between the center portion of the bent part and a wide end section. Thus, since a stress for making a biting motion (motion for cutting a nail) by folding the upper and lower cutters is concentrated upon a remaining portion of the minimum width centering around a hole of the bent part, there has been a problem that the expected life span of the cutter is considerably reduced.
Meanwhile, the prior art to which a hinge structure of a lever applied to the nail clipper of the invention is directed is disclosed in International Publication No. WO 02/39844. According to the nail clipper disclosed in International Publication No. WO 02/39844, oppositely disposed projections are a concave part formed with both side arms of the lever, a supporting shaft has a hooking groove formed by cutting off a part of both sides of an upper end of a cylinder, and the both projections serves to pulling the supporting shaft through leverage by assembling into the hooking grooves of the upper end of the cylinder. In such a case, a tension applied to the supporting shaft and the projection of the lever by leverage of the lever acts as a lateral force for biasing the projection toward the arm part, both arm parts are widened relative to each other, and thus there is a concern that they will be separated from the supporting shaft. Further, since the supporting shaft has the hooking groove formed by cutting off a part of both sides of an upper end of a cylinder, since, in case of enlarging the hooking groove, a remaining thickness of the cylinder should be reduced, the hooking groove cannot be enlarged, and thus the hooking part becomes considerably more fragile. In such a case, the projection of the lever can be separated from the supporting shaft even with some breakage or wear. This concern is greater when the lever is made of a plastic material.